Ordinary polarized relays have such structure that the center of the armature is pivotally supported so that the armature swings into contact with two contact pole surfaces of the yoke at diagonal positions.
Polarized relays of such structure have a problem that, unless three points at diagonally pole contacting surfaces and central pivot of the armature are maintained in dimensionally accurate relationship, there arises a phenomenon that only one of the pole contacting surfaces will achieve the contact and this will cause a beat to occur.
Thus, it has already been proposed to solve this problem by employing a structure in which the armature is moved horizontally back and forth.
For example, Japanese Patent Publication No. 41005/1980 (hereinafter referred to as the first prior art) has been proposed.
Referring to this with reference to FIG. 12, an E-shaped yoke 101 is formed with an upper piece 102, middle piece 103 and lower piece 104, a coil 105 is installed on the middle piece 103, and a permanent magnet 106 serving as an armature common to the upper, middle and lower pieces 102, 103 and 104 is opposed thereto, in which the magnetic flux of the permanent magnet 106 is in the direction indicated by X and that of the coil 105 is in the direction indicated by Y.
Therefore, the magnetic flux directions X and Y in gaps between the respective pieces 102, 103, 104 and the permanent magnet 106 are opposite to each other, that is, a repellent takes place and the permanent magnet 106 serving as the armature is moved horizontally in the direction of arrow Z.
When a coil current is subsequently made to flow so that the magnetic flux of the coil 105 will be in the opposite direction, this magnetic flux will be in the same direction as that X of the permanent magnet 106 and superposed on the latter, whereby the permanent magnet 106 being the armature is attracted.
In this polarized relay according to the first prior art, the magnetic flux induced by the coil 105 is made to pass through the permanent magnet 106, and there arises such problem that, since the permanent magnet 106 has a magnetic reluctance of about 10,000 times as high as that of ordinary yokes (iron) and involves a high percentage of loss in the magnetic flux induced by the coil 105, it is difficult to improve the sensitivity of the device.
To solve the problem described above, a polarized relay having such a structure as shown in French Pat. No. 2358006 (hereinafter referred to as the second prior art) has been further suggested.
This suggestion utilizes an advantage in the high sensitivity brought about by an arrangement in which the magnetic flux induced by the coil does not pass through the permanent magnet.
Referring thereto with reference to FIG. 13, two vertical magnetic pieces 202 and 203 and core 210a constitute a U-shaped yoke 201, while a permanent magnet 207, first magnetic piece 205 contacted with one pole of the permanent magnet and second magnetic piece 206 contacted with the other pole of the permanent magnet constitute an armature block 204, and the first magnetic piece 205 is formed in a U-shape having both end vertical pieces 208 and 209 opposed to the outer side surfaces of the vertical pieces 202 and 203 of the U-shaped yoke 201. The second magnetic piece 206 is opposed to the inner side surfaces of the vertical pieces 202 and 203 of the U-shaped yoke 201, and the permanent magnet 207 is held between the first and second magnetic pieces 205 and 206. A coil 210 is installed on the U-shaped yoke 201.
In this case of the second prior art, the magnetic flux X of the permanent magnet 207 flows through two magnetic paths from one pole of the permanent magnet 207 through the respective first and second magnetic pieces 205 and 206 of the armature bock 204 and back to the other pole of the permanent magnet 207 and through another magnetic path from the one pole of the permanent magnet 207 through the second magnetic piece 206 of the armature block 204, U-shaped yoke 201 and first magnetic piece 205 of the armature block 204 back to the other pole of the permanent magnet 207, while the magnetic flux of the coil 201 flows through a magnetic path through the core 210a, right-hand vertical piece 203 of the U-shaped yoke 201 (or the left-hand vertical piece 202 in the case when the armature block is reversed), first magnetic piece 205 of the armature block, permanent magnet 207, second magnetic piece 206 and left-hand vertical piece 202 of the U-shaped yoke 201 (or the left-hand vertical piece 203 when the armature block is reversed).
Therefore, when the directions X and Y of the magnetic fluxes in the gaps between the respective magnetic poles of the armature bock 204 and U-shaped yoke 201 are opposite to each other, a repellent takes place and, when the directions are the same, an attraction occurs, so that the armature block 204 will move horizontally in either direction depending upon the direction of the current flowing through the coil 210.
In this second prior art, the magnetic flux Y of the coil 210 does not flow through the permanent magnet 207 and the problem in the first prior art is solved.
However, the second prior art has another problem owing to the employment of the structure in which the permanent magnet is included in the armature block.
That is, because of the presence of the permanent magnet in the armature block, the operating speed of the armature block is slower by an amount corresponding to the weight of the permanent magnet 207, and eventual enlargement of the block results in a higher impact force and in a promotion of vibrations. Further, because of the gravity, the characteristics become unbalanced depending upon the direction in which the block is installed.
Another problem in the second prior art resides in that, as the yoke 201 is present only in the upper region of the armature block 204 and a spatial allowance is required to be present above and below the block with respect to guide means for its horizontal reciprocations, the block is pulled toward the yoke by an amount corresponding to such allowance at all times.
Therefore, the orientation of the yoke 201 changes depending upon the state in which the installation is made and, because of the weight of the armature block 204, the characteristics become also unbalanced as in the above.
Yet, any manner in which the horizontal reciprocation of the armature is practically realized in the polarized relay still has not been suggested and such realization should not be easy.
As a third prior art, there exists, for example, U.S. Pat. No. 2,794,882 but this is of a so-called non-polarized relay having no permanent magnet installed therein.